Czechoslovakia-Poland relations were immediately after their establishment influenced by the territorial dispute concerning the region of Teschen Silesia. The dispute lasted two years. What were the main causes of the conflict? Was the conflict caused by the mixed national composition on the territory of Teschen Silesia or by Czechoslovak and Polish political ambitions in Central and Eastern Europe? The study is based on the analysis of historical sources and scientific literature. It follows the formation of conflict lines and subsequent escalation of the conflict. Thesis is divided into two parts. First part represents internal dimension of the conflict, it focuses on the historical connection of Teschen Silesia and describes it as a distinctive territorial unit with special emphasis on selfperception of its inhabitants. It clarifies the mental shift from the identity which is perceived on the basis of social status to the identity based on the affiliation to the nation, which is later embodied by the establishment of Czechoslovakia and Poland. Second part of the Thesis turns its attention to the external, international dimension of the conflict, i.e. mutual Czechoslovak-Polish negotiations, genesis of their attitudes and the role of the Entente powers and decisive bodies of the Paris Peace...